Paired multi-layered dielectric independent passive component architecture resulting in differential and common mode filtering with surge protection in one integrated package

ABSTRACT

The present invention relates to a passive electronic component architecture employed in conjunction with various dielectric and combinations of dielectric materials to provide one or more differential and common mode filters for the suppression of electromagnetic emissions and surge protection. The architecture allows single or multiple components to be assembled within a single package such as an integrated circuit or connector. The component&#39;s architecture is dielectric independent and provides for integration of various electrical characteristics within a single component to perform the functions of filtering, decoupling, fusing and surge suppression, alone or in combination.

This application is a continuation-in-part of application Ser. No.09/008,769 filed Jan. 19, 1998 now U.S. Pat. No. 6,097,581 which is acontinuation-in-part of application Ser. No. 08/841,940 filed Apr. 8,1997 now U.S. Pat. No. 5,909,350.

TECHNICAL FIELD

The present invention relates to a filter for protecting electroniccircuitry from electromagnetic field interference (EMI), over voltagesand preventing electromagnetic emissions. More specifically, thisinvention relates to a multi-functional electronic component whosephysical architecture suppresses unwanted electromagnetic emissions,both those received from other sources and those created internallywithin electronic circuitry by differential and common mode currents. Inaddition, due to the electronic component's physical architecture andmaterial composition, over voltage surge protection and magneticproperties can be integrally incorporated with the differential andcommon mode filtering.

BACKGROUND OF THE INVENTION

The majority of electronic equipment produced presently, and inparticular computers, communication systems, automobiles, militarysurveillance equipment, stereo and home entertainment equipment,televisions and other appliances include miniaturized components toperform new high speed functions and electrical interconnections whichaccording to the materials from which they are made or their mere sizeare very susceptible to stray electrical energy created byelectromagnetic interference or voltage transients occurring onelectrical lines. Voltage transients can severely damage or destroy suchmicro-electronic components or contacts thereby rendering the electronicequipment inoperative, and requiring extensive repair and/or replacementat great cost.

Electrical interference in the form of EMI or RFI can be induced intoelectrical lines from such sources as radio broadcast antennas or otherelectromagnetic wave generators. EMI can also be generated from theelectrical circuit which is desired to be shielded from EMI.Differential and common mode currents are typically generated in cablesand on circuit board tracks. In many cases fields radiate from theseconductors which act as antennas. Controlling these conducted/radiatedemissions is necessary to prevent interference with other circuitry orother parts of the circuit generating or sensitive to the unwantednoise. Other sources of interference are generated from equipmentcoupled to the electrical lines, such as computers, switching powersupplies and a variety of other systems, which may generate significantinterference which is desired to be eliminated to meet internationalemission and/or susceptibility requirements.

Transient voltages occurring on electrical lines can be induced bylightning which produces extremely large potentials in a very shorttime. In a similar manner, nuclear electromagnetic pulses (EMP) generateeven larger voltage spikes with faster rise time pulses over a broadfrequency range which are detrimental to most electronic devices. Othersources of large voltage transients are found to be associated withvoltage surges occurring upon the switching off or on of some electronicpower equipment as well as ground loop interference caused by varyingground potentials. Existing protection devices, primarily due to theirarchitecture and basic materials, do not provide adequate protection ina single integrated package.

Based upon the known phenomenon of electromagnetic emissions andtransient voltage surges a variety of filter and surge suppressioncircuit configurations have been designed as is evident from the priorart. A detailed description of the various inventions in the prior artis disclosed in U.S. Pat. No. 5,142,430, herein incorporated byreference.

The '430 patent itself is directed to power line filter and surgeprotection circuit components and the circuits in which they are used toform a protective device for electrical equipment. The circuitcomponents comprise wafers or disks of material having desiredelectrical properties such as varistor or capacitor characteristics. Thedisks are provided with electrode patterns and insulating bands onsurfaces thereof which coact with apertures formed therein so as toelectrically connect the components to electrical conductors of a systemeasily and effectively. These electrode patterns act in conjunction withone another to form common electrodes with the material interposed therebetween. The '430 patent was primarily directed toward filtering pairedlines. The present invention improves on the paired line concept byrefining and adapting the concept for use with low voltage low currentdata communication lines as well as arrangements directed towards highvoltage industrial and home applications such as three phase powerlines, electric motor noise filtering, LANs and other computer andelectronic devices.

Therefore, in light of the foregoing deficiencies in the prior art, theapplicant's invention is herein presented.

SUMMARY OF THE INVENTION

Based upon the foregoing, there has been found a need to provide amulti-functioning electronic component which attenuates electromagneticemissions resulting from differential and common mode currents flowingwithin electronic circuits, single lines, pairs of lines and multipletwisted pairs. Because of the sensitive nature of electronic technologythere is also a need for combining electromagnetic filtering with surgeprotection to eliminate the susceptibility to over voltages andemissions from external sources. Due to the highly competitive nature oftoday's electronic industry such a differential and common modefilter/surge protector must be inexpensive, miniaturized, low in costand highly integrated to be incorporated into a plurality of electronicproducts.

It is therefore a main object of the invention to provide an easilymanufactured and adaptable multi-functional electronic component whichfilters electromagnetic emissions caused by differential and common modecurrents.

It is another object of the invention to provide a protective circuitarrangement which may be mass produced and adaptable to include one ormore protective circuits in one component package to provide protectionagainst voltage transients, over voltages and electromagneticinterference.

Another object of the invention is to provide protective circuits havingan inherent ground which provides a path for attenuating EMI and overvoltages without having to couple the hybrid electronic component tocircuit or earth ground.

These and other objects and advantages of the invention are accomplishedthrough the use of a plurality of common ground conductive platessurrounding corresponding electrode plates separated by a material whichexhibits any one or a combination of a number of predeterminedelectrical properties. By coupling pairs of conductors to the pluralityof common ground conductive plates and selectively coupling theconductors to electrode plates, line-to-line and line-to-groundcomponent coupling is accomplished providing differential and commonmode electromagnetic interference filtering and/or surge protection. Thecircuit arrangement comprises at least one line conditioning circuitcomponent constructed as a plate. Electrode patterns are provided on onesurface of the plate and the electrode surfaces are then electricallycoupled to electrical conductors of the circuit. The electrode patterns,dielectric material employed and common ground conductive plates producecommonality between electrodes for the electrical conductors whichproduces a balanced (equal but opposite) circuit arrangement with anelectrical component coupled line-to-line between the electricalconductors and line-to-ground from the individual electrical conductors.

The particular electrical effects of the differential and common modefilter are determined by the choice of material between the electrodeplates and the use of ground shields which effectively house theelectrode plates within one or more Faraday cages. If one specificdielectric material is chosen the resulting filter will be primarily acapacitive arrangement. The dielectric material in conjunction with theelectrode plates and common ground conductive plates will combine tocreate a line-to-line capacitor and a line-to-ground capacitor from eachindividual electrical conductor. If a metal oxide varistor (MOV)material is used then the filter will be a capacitive filter with overcurrent and surge protection characteristics provided by the MOV-typematerial. The common ground conductive plates and electrode plates willonce again form line-to-line and line-to-ground capacitive platesproviding differential and common mode filtering accept in the case ofhigh transient voltage conditions. During these conditions the MOV-typevaristor material, which is essentially a non-linear resistor used tosuppress high voltage transients, will take effect to limit the voltagewhich may appear between the electrical conductors.

In a further embodiment a ferrite material may be used adding additionalinherent inductance to the differential and common mode filterarrangement. As before, the common ground conductive and electrodeplates form line-to-line and line-to-ground capacitive plates with theferrite material adding inductance to the arrangement. Use of theferrite material also provides transient voltage protection in that itto will become conductive at a certain voltage threshold allowing theexcess transient voltage to be shunted to the common ground conductiveplates, effectively limiting the voltage across the electricalconductors.

Numerous other arrangements and configurations are also disclosed whichimplement and build on the above objects and advantages of the inventionto demonstrate the versatility and wide spread application ofdifferential and common mode filters within the scope of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded perspective view of a differential and commonmode filter in accordance with the present invention;

FIG. 1A shows an exploded perspective view of an alternate embodiment ofthe filter shown in FIG. 1;

FIG. 2 provides schematic diagrams of the filter shown in FIG. 1 withFIG. 2a being a pure schematic representation and FIG. 2b being aschematic representation of the physical architecture;

FIG. 3 is a logarithmic graph comparing the filter of FIG. 1 with afilter comprised of prior art chip capacitors showing insertion loss asa function of signal frequency;

FIG. 4 is an exploded perspective view of a multi-conductor differentialand common mode filter for use in connector applications;

FIG. 5 shows schematic representations of the differential and commonmode filter and prior art filters with FIG. 5a being a multi-capacitorcomponent as found in the prior art and FIG. 5b being the electricalrepresentation of the physical embodiment of the differential and commonmode filter of FIG. 4;

FIG. 6 is a top plan view of the plurality of common ground conductiveand electrode plates which make up a high density multi-conductordifferential and common filter embodiment;

FIG. 6A is a top plan view of the plurality of common ground conductiveand electrode plates which make up an alternate high densitymulti-conductor filter as shown in FIG. 6;

FIG. 7 is a front elevational view of an electrode plate where FIG. 7aand FIG. 7b are the front and back, respectfully, of the electrodeplate;

FIG. 8 shows a side elevational view of an alternative embodiment of thedifferential and common mode filter of FIG. 1 which employs theelectrode plates of FIG. 7;

FIG. 9 shows a front elevational view of the filter of FIG. 8;

FIG. 10 shows a surface mount chip embodiment of a differential andcommon mode filter with FIG. 10a being a perspective view and FIG. 11bshowing an exploded perspective view of the same;

FIG. 11 shows a further embodiment of the filter shown in FIG. 10 withFIG. 11a showing a perspective view in cut away of the filter and FIG.11b showing a schematic representation of the same;

FIG. 12 shows a multi-filter surface mount component with FIG. 12a beinga top plan view of the filter; FIGS. 12b through 12 d shows top planviews of internal electrode layers; and FIG. 12e shows a frontelevational view in cross section of the filter shown in FIG. 12a;

FIG. 13 is not included;

FIG. 14 is an exploded perspective view of the individual film plateswhich comprise a further embodiment of a differential and common modefilter;

FIG. 15 shows a front elevational view in cross-section of the filmplates of FIG. 14 in operable cooperation;

FIG. 16 shows a further alternative embodiment of the differential andcommon mode filter configured primarily for use with electric motors;FIG. 16a shows a top plan view of the motor filter embodiment; FIG. 16bshows a side elevational view of the same; FIG. 16c shows a sideelevational view in cross-section of the same; and FIG. 16d is anelectrical representation of the physical embodiment of the filter shownin FIG. 16a;

FIG. 17 shows the motor differential and common mode filter embodimentelectrically and physically coupled to an electric motor; FIG. 17a showsa top plan view of the filter coupled to a motor and FIG. 17b shows aside elevational view of the same;

FIG. 18 is a logarithmic graph showing a comparison of the emissionlevels in dBuV/m as a function of frequency for an electric motor with astandard filter and an electric motor with the differential and commonmode filter of FIG. 17;

FIG. 19 shows a further alternate embodiment of the motor differentialand common mode filter: FIG. 19a shows a top plan view of the pluralityof electrode plates; FIG. 19b shows an exploded perspective view of theelectrode plates electrically coupled to a plurality of electricalconductors; and FIG. 19c is an electrical representation of the physicalembodiment of the motor differential and common mode filter;

FIG. 20 shows a high power embodiment of the differential and commonmode filter with FIG. 20a being a schematic representation of the filterand FIG. 20b being a partial schematic/block diagram of the same;

FIG. 21 shows a high power differential and common mode filter with FIG.21a being a partially assembled perspective view and FIG. 21b being aschematic representation of the same;

FIG. 22 shows a further alternate embodiment of the present invention;FIG. 22a is an exploded prospective view of an alternate multi-conductordifferential and common mode filter for use in connector applications;FIG. 22b is a front elevational view of the filter shown in FIG. 22a;FIG. 22c is an electrical representation of the physical embodiment ofthe filter shown in FIG. 22a; and FIG. 22d is an alternate electricalrepresentation of the physical embodiment of the filter shown in FIG.22a;

FIG. 23 discloses one application of the filters of the presentinvention with FIG. 23a being an electrical representation of thephysical embodiment of independent surge and electromagneticinterference (EMI) devices in combination as shown in FIG. 23b;

FIG. 24 discloses a further application of the filters of the presentinvention with FIG. 24a being an electrical representation of thephysical embodiment of a surge protection device in combination with acapacitor as shown in FIG. 24b;

FIG. 25 discloses another application of the filters of the presentinvention with FIG. 25a being the physical embodiment of a differentialand common mode thru-hole filter in combination with a plurality ofsurge protection devices and FIG. 25b being an electrical representationof the combination shown in FIG. 25a, with FIG. 25c showing the top andbottom of the thru-hole filter;

FIG. 26 is an elevational view of an alternate embodiment of anelectrode plate where FIGS. 26a and 26 c are the front and back,respectively, of the electrode plate and FIG. 26b is a side elevationalview in cross section of the same electrode plate;

FIG. 27 is a side elevational view in cross section of an application inwhich two electrode plates, as shown in FIG. 26, are employed in anelectronic circuit;

FIG. 28 is a side elevational view in cross section of a furtherapplication in which two electrode plates, as shown in FIG. 26, and aground plane are employed in an electronic circuit;

FIG. 29 is an exploded view of the individual internal layers whichmakeup a multi-component strip filter wherein each internal layer shownis a bottom plan view of the layer;

FIG. 30 shows the multi-component strip filter shown in FIG. 29, whereFIG. 30a is a top plan view, FIG. 30b is front side elevational view,FIG. 30c is a back side elevational view and FIG. 30d is a bottom planview;

FIG. 31 is an exploded view of the individual internal layers whichmakeup an alternative multi-component strip filter wherein each internallayer shown is a bottom plan view of the layer;

FIG. 32 is an exploded view of the individual internal layers whichmakeup an alternative multi-component strip filter wherein each internallayer shown is a bottom plan view of the layer;

FIG. 33 shows the multi-component strip filter shown in FIG. 32, whereFIG. 33a is a top plan view, FIG. 33b is front side elevational view,FIG. 33c is a back side elevational view, FIG. 33d is a bottom plan viewand FIG. 33e is an end elevational view;

FIG. 34 is an exploded view of the individual internal layers whichmakeup an alternative multi-component strip filter wherein each internallayer shown is a bottom plan view of the layer;

FIG. 35 shows the multi-component strip filter shown in FIG. 34, whereFIG. 35a is a top plan view, FIG. 35b is front side elevational view,FIG. 35c is a back side elevational view, FIG. 35d is a bottom plan viewand FIG. 35e is an end elevational view;

FIG. 36 is an exploded view of the individual internal layers whichmakeup an alternative multi-component strip filter wherein each internallayer shown is a bottom plan view of the layer;

FIG. 37 shows the multi-component strip filter shown in FIG. 36, whereFIG. 37a is a top plan view, FIG. 37b is front side elevational view,FIG. 37c is a back side elevational view, FIG. 37d is a bottom plan viewand FIG. 37e is an end elevational view;

FIG. 38 is an exploded view of the individual internal layers whichmakeup multi-component filter wherein each internal layer shown is abottom plan view of the layer;

FIG. 39 is a schematic representation of the multi-component filtershown in FIG. 38; and

FIG. 40 is an isometric view of the multi-component filter shown in FIG.38 where FIG. 40a is a top plan view of the filter, FIG. 40b is a frontelevational view of the filter and FIG. 40c is a side elevational viewof the filter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Due to the continued and increasing use of electronics in daily life andthe amount of electromagnetic interference (EMI) and emissionsgenerated, new world electromagnetic compatibility (EMC) requirementsare being specified daily for use in such diverse applications as in thehome, hospitals, automotive, aircraft and satellite industries. Thepresent invention is directed towards a physical architecture for anelectronic component which provides EMI suppression, broad band I/O-linefiltering, EMI decoupling noise reduction and surge protection in oneassembly.

To propagate electromagnetic energy two fields are required, an electricand magnetic. Electric fields couple energy into circuits through thevoltage differential between two or more points. Magnetic fields coupleenergy into circuits through inductive coupling. Magnetic fieldsoriginate from currents flowing in a path which could simply consist ofa loop of wire. In such loops both fields exist and are also includedwithin circuit traces found on printed circuit boards. These fieldsstart to diverge at frequencies above 1 MHz.

As previously noted, propagated electromagnetic energy is the crossproduct of both electric and magnetic fields. Typically, emphasis isplaced on filtering EMI from circuit conductors carrying DC to highfrequency noise. This can be explained for two reasons, the first beingthat a changing electric field in free space gives rise to a magneticfield and second because a time varying magnetic flux will give rise toan electric field. As a result a purely electric or magnetic timevarying field cannot exist. Fields may be primarily electric orprimarily magnetic but neither can be generated exclusively.

The main cause of radiated emission problems are due to the two types ofconducted currents, differential and common mode. The fields generatedby these currents result in EMI emissions. Differential mode (DM)currents are those currents which flow in a circular path in wires,circuit board traces and other conductors in a manner in which the fieldrelated to these currents originates from the loop defined by theconductors.

Common and differential mode currents differ in that they flow indifferent circuit paths. Common mode noise currents are surfacephenomena relative to ground and, for example, travel on the outer skinof cables which are often grounded to the chassis. To reduce, minimizeor suppress the noise it is necessary to provide a low impedance path toground while simultaneously shortening the overall noise current loop.

Turning now to FIG. 1, an exploded perspective view of differential andcommon mode filter 10's physical architecture is shown. Filter 10 iscomprised of a plurality of common ground conductive plates 14 at leasttwo electrode plates 16 a and 16 b where each electrode plate 16 issandwiched between two common ground conductive plates 14. At least onepair of electrical conductors 12 a and 12 b is disposed throughinsulating apertures 18 or coupling apertures 20 of the plurality ofcommon ground conductive plates 14 and electrode plates 16 a and 16 bwith electrical conductors 12 a and 12 b also being selectivelyconnected to coupling apertures 20 of electrode plates 16 a and 16 b.Common ground conductive plates 14 consist entirely of a conductivematerial such as metal in the preferred embodiment. At least one pair ofinsulating apertures 18 are disposed through each common groundconductive plate 14 to allow electrical conductors 12 to pass throughwhile maintaining electrical isolation between common ground conductiveplates 14 and electrical conductors 12. The plurality of common groundconductive plates 14 may optionally be equipped with fastening apertures22 arranged in a predetermined and matching position to enable each ofthe plurality of common ground conductive plates 14 to be coupledsecurely to one another through standard fastening means such as screwsand bolts. Fastening apertures 22 may also be used to securedifferential and common mode filter 10 to another surface such as anenclosure or chassis of the electronic device filter 10 is being used inconjunction with.

Electrode plates 16 a and 16 b are similar to common ground conductiveplates 14 in that they are comprised of a conductive material and haveelectrical conductors 12 a and 12 b disposed through apertures. Unlikecommon ground conductive plates 14, electrode plates 16 a and 16 b areselectively electrically connected to one of the two electricalconductors 12. While electrode plates 16, as shown in FIG. 1, aredepicted as smaller than common ground conductive plates 14 this is notrequired but in this configuration has been done to prevent electrodeplates 16 from interfering with the physical coupling means of fasteningapertures 22.

Electrical conductors 12 provide a current path which flows in thedirection indicated by the arrows positioned at either end of theelectrical conductors 12 as shown in FIG. 1. Electrical conductor 12 arepresents an electrical signal conveyance path and electrical conductor12 b represents the signal return path. While only one pair ofelectrical conductors 12 a and 12 b is shown, Applicant contemplatesdifferential and common mode filter 10 being configured to providefiltering for a plurality of pairs of electrical conductors creating ahigh density multiconductor differential and common mode filter.

The final element which makes up differential and common mode filter 10is material 28 which has one or a number of electrical properties andsurrounds the center common ground conductive plate 14, both electrodeplates 16 a and 16 b and the portions of electrical conductors 12 a and12 b passing between the two outer common ground conductive plates 14 ina manner which completely isolates all of the plates and conductors fromone another except for the connection created by the conductors 12 a and12 b and coupling aperture 20. The electrical characteristics ofdifferential and common mode filter 10 are determined by the selectionof material 28. If a dielectric material is chosen filter 10 will haveprimarily capacitive characteristics. Material 28 may also be a metaloxide varistor material which will provide capacitive and surgeprotection characteristics. Other materials such as ferrites andsintered polycrystalline may be used wherein ferrite materials providean inherent inductance along with surge protection characteristics inaddition to the improved common mode noise cancellation that resultsfrom the mutual coupling cancellation effect. The sinteredpolycrystalline material provides conductive, dielectric, and magneticproperties. Sintered polycrystalline is described in detail in U.S. Pat.No. 5,500,629 which is herein incorporated by reference.

An additional material that may be used is a composite of highpermittivity ferro-electric material and a high permeabilityferromagnetic material as disclosed in U.S. Pat. No. 5,512,196 which isincorporated by reference herein. Such a ferroelectric-ferromagneticcomposite material can be formed as a compact unitary element whichsingularly exhibits both inductive and capacitive properties so as toact as an LC-type electrical filter. The compactness, formability andfiltering capability of such an element is useful for suppressingelectromagnetic interference. In one embodiment the ferroelectricmaterial is barium titanate and the ferromagnetic material is a ferritematerial such as one based upon a copper zinc ferrite. The capacitiveand inductive characteristics of the ferroelectric-ferromagneticcomposites exhibit attenuation capabilities which show no signs ofleveling off at frequencies as high as 1 Ghz. The geometry of theferroelectric-ferromagnetic composite will significantly effect theultimate capacitive and inductive nature of an electrical filter thatemploys such a composite. The composite can be adjusted during itsmanufacturing process to enable the particular properties of a filter tobe tuned to produce suitable attenuation for specific applications andenvironments.

Still referring to FIG. 1, the physical relationship of common groundconductive plates 14, electrode plates 16 a and 16 b, electricalconductors 12 a and 12 b and material 28 will now be described in moredetail. The starting point is center common ground conductive plate 14.Center plate 14 has the pair of electrical conductors 12 disposedthrough their respective insulating apertures 18 which maintainelectrical isolation between common ground conductive plate 14 and bothelectrical conductors 12 a and 12 b. On either side, both above andbelow, of center common ground conductive plate 14 are electrode plates16 a and 16 b each having the pair of electrical conductors 12 a and 12b disposed there through. Unlike center common ground conductive plate14, only one electrical conductor, 12 a or 12 b, is isolated from eachelectrode plate, 16 a or 16 b, by an insulating aperture 18. One of thepair of electrical conductors, 12 a or 12 b, is electrically coupled tothe associated electrode plate 16 a or 16 b respectively throughcoupling aperture 20. Coupling aperture 20 interfaces with one of thepair of electrical conductors 12 through a standard connection such as asolder weld, a resistive fit or any other method which will provide asolid and secure electrical connection. For differential and common modefilter 10 to function properly, upper electrode plate 16 a must beelectrically coupled to the opposite electrical conductor 12 a than thatto which lower electrode plate 16 b is electrically coupled, that beingelectrical conductor 12 b. Differential and common mode filter 10optionally comprises a plurality of outer common ground conductiveplates 14. These outer common ground conductive plates 14 provide asignificantly larger ground plane which helps with attenuation ofradiated electromagnetic emissions and provides a greater surface areain which to dissipate over voltages and surges. This is particularlytrue when plurality of common ground conductive plates 14 are notelectrically coupled to circuit or earth ground but are relied upon toprovide an inherent ground. As mentioned earlier, inserted andmaintained between common ground conductive plates 14 and both electrodeplates 16 a and 16 b is material 28 which can be one or more of aplurality of materials having different electrical characteristics.

FIG. 1A shows an alternative embodiment of filter 10 which includesadditional means of coupling electrical conductors or circuit boardconnections to filter 10. Essentially, the plurality of common groundconductive plates 14 are electrically connected to an outer edgeconductive band or surface 14 a. Also each electrode plate 16 a and 16 bhas its own outer edge conductive band or surface, 40 a and 40 brespectively. To provide electrical connections between electrode plate16 a and 16 b and their respective conductive band 40 a and 40 b whileat the same time maintaining electrical isolation between other portionsof filter 10, each electrode plate 16 is elongated and positioned suchthat the elongated portion of electrode plate 16 a is directed oppositeof the direction electrode plate 16 b is directed. The elongatedportions of electrode plates 16 also extend beyond the distance in whichthe plurality of common ground conductive plates 14 extend with theadditional distance isolated from outer edge conductive bands 40 a and40 b by additional material 28. Electrical connection between each ofthe bands and their associated plates is accomplished through physicalcontact between each band and its associated common ground conductive orelectrode plate.

FIG. 2 shows two representations of differential and common mode filter10. FIG. 2a is a schematic representation demonstrating that filter 10provides a line-to-line capacitor 30 between and coupled to electricalconductors 12 a and 12 b and two line-to-ground capacitors 32 eachcoupled between one of the pair of the electrical conductors 12 andinherent ground 34. Also shown in dashed lines is inductance 36 which isprovided if material 28 is comprised of a ferrite material, as describedin more detail later.

FIG. 2b shows a quasi-schematic of the physical embodiment of filter 10and how it correlates with the capacitive components shown in FIG. 2a.Line-to-line capacitor 30 is comprised of electrode plates 16 a and 16 bwhere electrode plate 16 a is coupled to one of the pair of electricalconductors 12 a with the other electrode plate 16 b being coupled to theopposite electrical conductor 12 b thereby providing the two parallelplates necessary to form a capacitor. Center common ground conductiveplate 14 acts as inherent ground 34 and also serves as one of the twoparallel plates for each line-to-ground capacitor 32.

The second parallel plate required for each line-to-ground capacitor 32is supplied by the corresponding electrode plate 16. By carefullyreferencing FIG. 1 and FIG. 2b, the capacitive plate relationships willbecome apparent. By isolating center common ground conductive plate 14from each electrode plate 16 a or 16 b with material 28 havingelectrical properties, the result is a capacitive network having acommon mode bypass capacitor 30 extending between electrical conductors12 a and 12 b and line-to-ground decoupling capacitors 32 coupled fromeach electrical conductor 12 a and 12 b to inherent ground 34.

Inherent ground 34 will be described in more detail later but for thetime being it may be more intuitive to assume that it is equivalent toearth or circuit ground. To couple inherent ground 34, which center andadditional common ground conductive plates 14 form, one or more ofcommon ground conductive plates 14 are coupled to circuit or earthground by common means such as a soldering or mounting screws insertedthrough fastening apertures 22 which are then coupled to an enclosure orgrounded chassis of an electrical device. While differential and commonmode filter 10 works equally well with inherent ground 34 coupled toearth or circuit ground, one advantage of filter 10's physicalarchitecture is that a physical grounding connection is unnecessary.

Referring again to FIG. 1 an additional feature of differential andcommon mode filter 10 is demonstrated by clockwise and counterclockwiseflux fields, 24 and 26 respectively. The direction of the individualflux fields is determined and may be mapped by applying Ampere's Law andusing the right hand rule. In doing so an individual places their thumbparallel to and pointed in the direction of current flow throughelectrical conductors 12 a or 12 b as indicated by the arrows at eitherends of the conductors. Once the thumb is pointed in the same directionas the current flow, the direction in which the remaining fingers on theperson's hand curve indicates the direction of rotation for the fluxfields. Because electrical conductors 12 a and 12 b are positioned nextto one another and represent a single current loop as found in many I/Oand data line configurations, the currents entering and leavingdifferential and common mode filter 10 are opposed thereby creatingopposed flux fields which cancel each other and minimize inductance. Lowinductance is advantageous in modem I/O and high speed data lines as theincreased switching speeds and fast pulse rise times of modem equipmentcreate unacceptable voltage spikes which can only be managed by lowinductance surge devices.

It should also be evident that labor intensive aspects of usingdifferential and common mode filter 10 as compared to combining discretecomponents found in the prior art provides an easy and cost effectivemethod of manufacturing. Because connections only need to be made toeither ends of electrical conductors 12 to provide a differential modecoupling capacitor and two common mode decoupling capacitors, time andspace are saved.

FIG. 3 shows a comparison of the change in insertion loss relative tofrequency of several chip capacitors of the prior art versusdifferential and common mode filter 10 of the present invention. Thegraph shows that chip capacitor 50 configured line-to-line with a valueof 82 pF or chip capacitor 56 having a value of 82 pF but configuredline-to-ground, both demonstrate varying non-linear characteristics. Onthe other hand filter 10 configured in any of the following waysdemonstrates significantly lower linear insertion losses even up tofrequencies of 100 MHZ: (1) with line-to-line capacitor 54 having avalue of 82 pF as compared to conventional capacitor 50 having the samevalue; (2) with line-to-ground capacitor 58 having a value of 82 pF ascompared to conventional capacitor 56 having the same value; and (3)line-to-ground capacitor 52 having a value of 41 pF as compared to bothconventional capacitors 50 and 56.

An alternate embodiment of the present invention is differential andcommon mode multi-conductor filter 110 shown in FIG. 4. Filter 110 issimilar to filter 10 of FIGS. 1 and 1A in that it is comprised of aplurality of common ground conductive plates 112 and a plurality ofconductive electrodes 118 a thru 118 h to form differential modecoupling capacitors and common mode decoupling capacitor arrangementswhich act on a plurality of pairs of electrical conductors, not shown inFIG. 4 but similar to electrical conductors 12 a and 12 b shown in FIGS.1 and 1A. As described earlier for the single pair conductor filter 10shown in FIG. 1, common ground conductive plates 112, conductiveelectrodes 118 and the plurality of electrical conductors are isolatedfrom one another by a pre-selected material 122 having predeterminedelectrical characteristics such as dielectric material, ferritematerial, MOV-type material and sintered polycrystalline material. Eachof the plurality of common ground conductive plates 112 has a pluralityof insulating apertures 114 in which electrical conductors pass whilemaintaining electrical isolation from the respective common groundconductive plates 112. To accommodate a plurality of electricalconductor pairs, differential and common mode filter 110 must employ amodified version of the electrode plates described in FIGS. 1 and 1A.

To provide multiple independent conductive electrodes for each pair ofelectrical conductors, a support material 116 comprised of one of thematerials 122 containing desired electrical properties is used. Supportplate 116 a is comprised of a plurality of conductive electrodes 118 b,118 c, 118 e and 118 h printed upon one side of plate 116 a with onecoupling aperture 120 per electrode. Support plate 116 b is alsocomprised of a plurality of conductive electrodes 118 a, 118 d, 118 fand 118 g printed upon one side of plate 116 b. Support plates 116 a and116 b are separated and surrounded by a plurality of common groundconductive plates 112. The pairs of incoming electrical conductors eachhave a corresponding electrode pair within filter 110. Although notshown, the electrical conductors pass through the common groundconductive plates 112 and the respective conductive electrodes.Connections are either made or not made through the selection ofcoupling apertures 120 and insulating apertures 114. The common groundconductive plates 112 in cooperation with conductive electrodes 118 athru 118 h perform essentially the same function as electrode plates 16a and 16 b of FIGS. 1 and 1A.

FIG. 5 shows schematic diagrams of prior art multi-capacitor componentsand differential and common mode multi-conductor filter 110 of thepresent invention. FIG. 5a is a schematic of prior art capacitor array130. Essentially, a plurality of capacitors 132 are formed and coupledto one another to provide common ground 136 for array 130 with openterminals 134 provided for connecting electrical conductors to eachcapacitor 132. These prior art capacitor arrays only allowed common modedecoupling of individual electrical conductors when open terminal 134 ofeach capacitor 132 was electrically connected to individual electricalconductors.

FIG. 5b shows a schematic representation of differential and common modemulticonductor filter 110 having four differential and common modefilter pin pair pack arrangements. The horizontal line extending througheach pair of electrodes represents the common ground conductive plates112 with the lines encircling the pairs being the isolation bars 112 a.The isolation bars 112 a are electrically coupled to common groundconductive plates 112 providing an inherent ground grid separating eachof the electrode plates 118 a through 118 h from one another. Thecorresponding conductive electrodes 118 a thru 118 h positioned onsupport material plates 116 a and 116 b, both above and below the centercommon ground conductive plate 112, and form line-to-ground common modedecoupling capacitors. Each plate, common ground plates 112 and supportmaterial plates 116 a and 116 b, is separated from the others bydielectric material 122. When filter 110 is connected to pairedelectrical conductors via coupling apertures 120 such as those found inelectrode plates 118 a and 118 c, filter 110 forms a line-to-linedifferential mode filtering capacitor.

Again referring to FIG. 4, multi-conductor filter 110 is shown havingnot only a center common ground conductive plate 112 but outer commonground conductive plates 112. As described in relation to FIGS. 1 and 1Athese outer common ground conductive plates 112 provide a significantlylarger ground plane for filter 110 which helps with attenuation ofradiated electromagnetic emissions, provides a greater surface area todissipate and/or absorb over voltages, surges and noise, and effectivelyacts as a Faraday shield. This is particularly true when plurality ofcommon ground conductive plates 112 are not electrically connected tocircuit or earth ground but are instead relied upon to provide aninherent ground.

A further variation of the present invention is differential and commonmode multiconductor filter 680 shown in FIG. 22. Filter 680 has beenoptimized for use with computer and telecommunications equipment and inparticular has been configured for use with RJ 45 connectors. To obtainimproved filters performance, filter 680 includes built in chassis andcircuit board low frequency noise blocking capacitors in addition to aplurality of differential and common mode filters. As shown in FIG. 22a,the physical construction of filter 680 is substantially similar tofilter 110, shown in FIG. 4, and is comprised of a plurality of commonground conductive plates 112, first and second electrode plates 676 and678 having a plurality of conductive electrodes to form multipledifferential and common mode filters including chassis and boardblocking capacitors. As described for earlier embodiments, common groundconductive plates 112, conductive electrodes 686, 688, 690 and 692,blocking electrodes 682 and 684, and the electrical conductors (notshown) which pass through the various plates are all isolated from oneanother by material 122. To realize particular predetermined electricalcharacteristics in filter 680, as in all other embodiments of thepresent invention, material 122 can consist of dielectrics, ferrites,MOV-type material or sintered polycrystaline. Each common groundconductive plate 112 includes a plurality of insulating apertures 114 inwhich electrical conductors pass while maintaining electrical isolationfrom common ground. conductive plate 112. To obtain the additionalchassis and board noise blocking capacitors, filter 680 employs amodified version of the electrode plates of FIG. 1.

As described for FIG. 4, to provide multiple independent components fora number of pairs of electrical conductors, material 122 also serves assupport material 116 which is used to fabricate first and secondelectrode plates 676 and 678. First electrode plate 676 is made up offirst and second conductive electrodes 682 and 686 and blockingelectrode 688, all printed upon one side of support material 116. Secondelectrode plate 678 is made up of first and second conductive electrodes684 and 690 and blocking electrode 692, again printed upon one side ofsupport material 116. First and second electrode plates 676 and 678 arethen separated and surrounded by common ground conductive plates 112.What differs in filter 680 from previous embodiments which allows forthe combination of differential and common mode filters with built inchassis and board noise blocking capacitors is the configuration offirst and second conductive electrodes and blocking electrodes on firstand second electrode plates 676 and 678. First and second conductiveelectrodes 686 and 688 of first electrode plate 676 each include onecoupling aperture 120 disposed in the electrode. Blocking electrode 682is formed to partially surround first and second conductive electrodes686 and 688 and includes a plurality of insulating apetures 114 andcoupling apertures 120. Second electrode plate 678 is identical to firstelectrode plate 676 with first and second conductive electrodes 690 and692 corresponding to first and second conductive electrodes 686 and 688and blocking electrode 684 corresponding with blocking electrode 682. Asis clearly shown in FIG. 22a, when coupled between the various commonground conductive plates 112, first and second electrode plates 676 and678 are arranged in opposite directions from one another. Thisparticular alignment of first and second electrode plates 676 and 678allows filter 680 to have a traditional RJ 45 pinout configuration whenused in a connector application. It should be noted that Applicantcontemplates other configurations of conductive and blocking electrodesdepending upon the desired pinout or wiring arrangement desired and theinverted arrangement of first and second electrode plates 676 and 678 isnot required.

As in other embodiments, a number of electrical conductors will passthrough common ground conductive plates 112 and first and secondelectrode plates 676 and 678. Although the electrical conductors areabsent, FIG. 22b shows that this particular embodiment of filter 680 isadapted to accept eight conductors in accordance with RJ 45 connectorstandards. The interaction of the various conductive electrodes withinfilter 680 will now be described by refering FIGS. 22a through 22 d withFIG. 22b included to further correlate the electrical representationwith the physical embodiment of filter 680. FIG. 22d is an alternateelectrical representation of filter 680 which should also be referred toas needed. Signal ground (SG) for filter 680 is provided by thecombination of common ground conductive plates 112 which act as aninherent ground. The physical separation of the various conductiveelectrodes of first and second electrode plates 676 and 678 by theconductive plane of common ground conductive plates 112 provides asubstantial ground plane for filter 680 which inherently acts as aground and assists with attenuation of radiated electromagneticadmissions, provides a greater surface area to dissipate and/or absorbover voltages, surges and noise, and effectively acts as a Faradayshield protecting the filter from external electrical noise andpreventing radiation of the same by filter 680.

Referring to the various electrical conductors (not shown) by thenumbers 1 through 8 as shown in FIGS. 22b, 22 c and 22 d, the electricalconductors 3 and 5 are connected through coupling apetures 120 to firstand second conductive electrodes 686 and 688 respectively. Electricalconductors 4 and 6 are connected through coupling apetures 120 toconductive electrodes 690 and 692 respectively. Conductors 1 and 7 areconnected through coupling apetures 120 to blocking electrode 684 andelectrical conductors 2 and 8 are similarly connected through couplingapetures 120 to blocking electrode 682. Referring to FIG. 22d,electrical conductors 3 and 6 are filtered differentially by theinteraction of first and second conductive electrodes 686 and 692 whichact as opposing plates to form a line-to-line capacitor betweenelectrical conductors 3 and 6. The same electrical conductors eachreceive common mode filtering through line-to-ground capacitors formedby the interaction of first and second conductive electrodes 686 and 692with common ground conductive plates 112 which forms line-to-groundcapacitors between each electrical conductor and the inherent groundformed by the plurality of common ground conductive plates 112.

The same relationship exists for electrical conductors 4 and 5 which areconnected to first and second conductive electrodes 690 and 688respectively. First and second conductive electrodes 690 and 688 formline-to-line capacitors and each interacts with common ground conductiveplates 112 to form individual common mode filter capacitors for eachelectrical conductor. In addition to the plurality of differential andcommon mode filters created by the interaction between the variousconductive electrodes and common ground conductive plates, chassis andboard noise blocking capacitors are also formed by the interaction ofcommon ground conductive plates 112 and blocking electrodes 682 and 684.For instance, chassis ground is connected to the electrical conductors 1and 7, both of which are electrically connected through couplingapetures 120 to blocking electrode 682 thereby forming one plate of thenoise blocking capacitors. The other plate of the noise blockingcapacitors is formed by common ground conductive plates 112 whichinteract with blocking electrode 682. Although interchangeable,electrical conductors 2 and 8 also provide board noise blockingcapacitors formed by the interaction of common ground conductive plates112 and blocking electrode 682. Both the chassis and board blockingnoise capacitors allow the inherent ground formed by common groundconductive plates 112 to be capacitively decoupled thereby blocking lowfrequency electrical noise from the signal carrying conductors. Thisimproves differential and common mode filter performance by essentiallyelectrically cleansing the inherent ground formed by common groundconductive plates 112.

FIG. 6 illustrates a further embodiment of the present invention whichprovides input/output data line pair filtering for a large number ofelectrical conductor pairs typical of todays high density informationand data buses. Differential and common mode high density filter 150 iscomprised of a plurality of common ground conductive plates 112containing a plurality of insulating apertures 114 and conductiveelectrode plates 116 a and 116 b each having electrode patterns 118,insulating apertures 114 and coupling apertures 120. The stackingsequence is reflected in FIG. 6 recognizing that dielectric materialwill surround each of the individual plates as described for previousembodiments.

FIG. 6A presents an alternative approach in which differential andcommon mode high density filter 150 utilizes a tri-coupling of theelectrodes to develop a higher capacitance to ground and line-to-line.Again, filter 150 is comprised of a plurality of common groundconductive plates 112 each having a plurality of insulating apertures114, conductive electrode plates 119 a thru 119 c with their respectiveelectrode patterns 117 a thru 117 c. Each conductive electrode plate,119 a through 119 c, contains a plurality of insulating apertures 114and coupling apertures 120 in predetermined positions to allow pairs ofelectrical conductors to pass through while selectively coupling theelectrical conductors to create the desired filter architecture. Thestacking sequence of the plates shown in FIG. 6A is again similar tothose shown for FIGS. 1, 1A, 4 and 6 and again a predetermineddielectric material 122 surrounds each of the individual plates invarying thicknesses.

FIGS. 7, 8 and 9 show single aperture electrode plate 70 and the use ofa plurality of such plates in an alternative embodiment of thedifferential and common mode filter of the present invention. FIG. 7shows the two sides of electrode plate 70 with FIG. 7a being the frontand FIG. 7b being the back. Referring to FIG. 7a, electrode plate 70 iscomprised of material 72 having predetermined electrical properties,such as a dielectric or other material as described earlier, wherematerial 72 is molded into a desired shape which in this case is a disk.Aperture 78 is disposed through electrode plate 70 to allow anelectrical conductor to pass. The front of electrode plate 70 ispartially covered by conductive surface 74 to create isolation band 82about the outer perimeter of electrode plate 70. Surrounding aperture 78is solder band 80 which, once heated, will adhere to an electricalconductor disposed through aperture 78 and electrically connect theconductor to conductive surface 74. Referring now to FIG. 7b, thebackside of electrode plate 70 is similar to the front side in thatconductive surface 74 is adhered to material 72 in such a fashion as toprovide isolation band 82 around its outer perimeter. Differing from thefront side, aperture 78 is surrounded by isolation band 76 to preventany electrical connection between electrical conductors and conductivesurface 74 of the backside of electrode plate 70.

FIGS. 8 and 9 demonstrate how multiple electrode plates 70 are used tocreate differential and common mode filter 90. The construction offilter 90 is similar to previous embodiments in that common groundconductive plate 98 is sandwiched between at least two electrode plates70 to provide the parallel plate arrangement necessary to form aplurality of capacitive elements. As shown in FIG. 9, one electrodeplate 70 is coupled to one side of common ground conductive plate 98with a second electrode plate 70 being coupled to the opposite side ofplate 98 and offset a distance great enough to allow electricalconductors 92 a and 92 b to pass through one electrode plate 70 withoutinterference from the other electrode plate 70 coupled to the oppositeside of common ground conductive plate 98. Although not clearly shown itshould be apparent that common ground conductive plate 98 includesapertures in predetermined positions which correspond with theassociated apertures of electrode plates 70 to allow electricalconductors 92 a and 92 b to pass through as shown in FIG. 8.

Common ground conductive plate 98 serves as and provides inherent ground96, which may be connected to earth or signal ground if desired.Fastening apertures 22 allow filter 90 to be mechanically coupled to astructure. One means of physically coupling electrode plate 70 to commonground conductive plate 98 is shown in FIG. 8. Sandwiched between commonground conductive plate 98 and electrode plate 70's backside is solderweld 84 which when heated adheres to conductive surface 74 of thebackside of electrode plate 70 and the corresponding surface of commonground conductive plate 98. When connecting electrode plate 70 to commonground conductive plate 98, electrode plate 70's backside always facesthe corresponding side of common ground conductive plate 98. The samemechanical coupling means is used for both electrode plates. Solder band80 is also shown for each electrode plate 70 which only couples one ofthe two electrical conductors 92 a and 92 b, to their respectiveelectrode plates. The arrangement of common ground conductive plate 98and electrode plates 70 provides line-to-line differential modefiltering between and line-to-ground decoupling for each electricalconductor 92 a and 92 b. The differential mode filtering is accomplishedby conductive surfaces 74 of the front sides of both electrode plates 70which act as the parallel plates of a capacitor coupled betweenelectrical conductors 92 a and 92 b or line-to-line. The line-to-grounddecoupling is provided by conductive surfaces 74 of each electrode plate70 acting as one capacitive plate and common ground conductive plate 98acting as the other parallel capacitive plate. The parallel capacitiveplate provided by common ground conductive plate 98, which serves asinherent ground 96, provides the ground decoupling connection for eachelectrical conductor, 92 a and 92 b.

Differential and common mode filter 90 shown in FIGS. 8 and 9 isadvantageous in that its construction is relatively simple and itsvoltage and current handling capacities are only limited by its physicalstructure which may easily be enlarged or reduced depending upon thedesired characteristics.

FIGS. 26, 27 and 28 disclose double aperture electrode plate 600 and theuse of a plurality of such plates in further alternative embodiments ofthe differential and common mode filters of the present invention.Referring to FIG. 26a, electrode plate 600 is comprised of material 616having predetermined electrical properties, with material 616 beingmolded into a desired shape shown here as being a disk. A first side ofdouble aperture electrode plate 600 is shown in FIG. 26a and includesfirst and second apertures 602 and 604 each including an isolation band606 which separates the apertures from first conductive surface 608. Asecond side of double aperture electrode plate 600 is shown in FIG. 26cand includes first aperture 602 having isolation band 606 and secondaperture 604 directly connected to second conductive surface 610 whichspans most of the second side of double aperture electrode plate 600,with the exception of isolation band 612 which runs along the outerperimeter of plate 600. FIG. 26b shows first conductive surface 608 iselectrically coupled to side conductive surface 614 which encirclesdouble aperture electrode plate 600. Isolation band 612, located alongthe perimeter of the second side of double aperture electrode plate 600,physically separates and electrically isolates first and secondconductive surfaces 608 and 610 from one another.

When two electrical conductors pass through first and second apertures602 and 604, only the electrical conductor passing through aperture 604will be electrically connected to second conductive surface 610. Thefunction of double aperture electrode plate 600 is identical to singleaperture electrode plate 70 shown in FIG. 7 with the only differencebeing electrode plate 600 does not have to be arranged in an offsetmanner to allow passage of opposing electrical conductors as was shownand described for FIG. 9.

FIG. 27 shows how multiple double aperture electrode plates 600 are usedto create differential and common mode filter 626 which is accomplishedby electrically connecting two double aperture electrode plates 600 sothe first side of each electrode plate 600, shown in FIG. 26a, faces thefirst side of the opposing electrode plate 600 with first conductivesurface 608 of each electrode plate 600 electrically connected throughmeans known in the art such as solder 622 melted between the two firstconductive surfaces 608. Two electrical conductors, 618 and 620, passthrough the aligned apertures of each double aperture electrode plate600 with electrical conductor 618 electrically connected to secondconductive surface 610 b of electrode plate 600 b and electricalconductor 620 electrically connected to second conductive surface 610 aof electrode plate 600 a. Following the same principles set forth forthe differential and common mode architecture of the present invention,first conductive surfaces 608 a and 608 b form and act as a commonground conductive plate which provides an inherent ground fordifferential and commode mode filter 626. Second conductive surfaces 610a and 610 b of each electrode plate 600 a and 600 b act as theindividual conductive electrodes forming two plates which make up adifferential capacitor coupled between electrical conductors 618 and620. Second conductive surfaces 610 a and 610 b also form common modedecoupling capacitors when taken in conjunction with first conductivesurfaces 608 a and 608 b which act as the inherent ground. One advantageto double aperture electrode plate 600, as compared to the singleaperture electrode plate 70 shown in FIG. 7, is that a separate commonground conductive plate is unnecessary. First conductive surfaces 608 aand 608 b act as and form the common ground conductive plate. Ifdesired, a separate common ground conductive plate 624 having alignedinsulated apertures may be positioned between double aperture electrodeplates 600 a and 600 b, as shown in FIG. 28, to provide an enhancedinherent ground with a greater conductive area for distributingelectrical noise and heat.

One trend found throughout modem electronic devices is the continuousminiaturization of equipment and the electronic components which make upthat equipment. Capacitors, the key component in differential and commonmode filter arrangements, have been no exception and their size hascontinually decreased to the point where they may be formed in siliconand imbedded within integrated circuits only seen with the use of amicroscope. One miniaturized capacitor which has become quite prevalentis the chip capacitor which is significantly smaller than standardthrough hole or leaded capacitors. Chip capacitors employ surface mounttechnology to physically and electrically connect to electricalconductors and traces found on circuit boards. The versatility of thearchitecture of the differential and common mode filter of the presentinvention extends to surface mount technology as shown in FIG. 10.Surface mount differential and common mode filter 400 is shown in FIG.10a with its internal construction shown in FIG. 10b. Referring to FIG.10b, common ground conductive plate 412 is sandwiched between firstdifferential plate 410 and second differential plate 414. Common groundconductive plate 412 and first and second differential plates 410 and414 are each comprised of material 430 having desired electricalproperties dependant upon the material chosen. As for all embodiments ofthe present invention, Applicant contemplates the use of a variety ofmaterials such as but not limited to dielectric material, MOV-typematerial, ferrite material, film such as Mylar and newer exoticsubstances such as sintered polycrystalline.

First differential plate 410 includes conductive electrode 416 coupledto the top surface of material 430 in a manner which leaves isolationband 418 surrounding the outer perimeter of first differential plate 410along three of its four sides. Isolation band 418 is simply a portionalong the edge of material 430 that has not been covered by conductiveelectrode 416. Second differential plate 414 is essentially identical tofirst differential plate 410 with the exception being its physicalorientation with respect to that of first differential plate 410. Seconddifferential plate 414 is comprised of material 430 having conductiveelectrode 426 coupled to the top surface of material 430 in such amanner as to leave isolation band 428 surrounding the outer perimeter ofsecond differential plate 414 along three of its four sides. What isimportant to note about first and second differential plates 410 and414's physical orientation with respect to one another is that the oneside of each plate in which isolation bands 418 and 428 do notcircumscribe are arranged 180° apart from one another. This orientationallows each electrical conductor to be coupled to either individualplate 410 or 414 but not both.

Common plate 412 is similar in construction to first and seconddifferential plates 410 and 414 in that it to includes material 430 withcommon conductive electrode 424 coupled to its top surface. As can beseen from FIG. 10b, common plate 412 has two isolation bands 420 and 422positioned at opposite ends. Common plate 412 is aligned in betweenfirst and second differential plates 410 and 414 so that isolation bands420 and 422 are aligned with the ends of first and second differentialplates 410 and 414 which do not have isolation bands. All three plates,common plate 412 and first and second differential plates 410 and 414 donot have any type of conductive surface beneath each plate and thereforewhen the plates are stacked one on top of the other, conductiveelectrode 426 is isolated from common conductive electrode 424 by thebackside of common plate 412. In a similar fashion common conductiveelectrode 424 is isolated from conductive electrode 416 by the backsideof first differential plate 410 which is comprised of material 430.

Referring now to FIG. 10a the construction of surface mount differentialand common mode filter 400 will be further described. Once common plate412 and first and second differential plates 410 and 414 are sandwichedtogether according to the arrangement shown in FIG. 10b, a means forcoupling electrical conductors to the different electrodes must beincluded. Electrical conductors are coupled to surface mountdifferential and common mode filter 400 through first differentialconductive band 404 and second differential conductive band 406 whichare isolated from common conductive band 402 by isolation bands 408positioned in between bands 402, 404 and 406. Common conductive band 402and isolation bands 408 extend 360° around the body of filter 400 toprovide isolation on all four sides. First and second differentialconductive bands 404 and 406 not only extend 360° around filter 400 butalso extend to cover ends 432 and 434, respectively.

By referring back and forth between FIGS. 10a and 10 b, the couplingbetween the bands and the plates can be seen. First differentialconductive band 404 including end 434 maintains electrical coupling withconductive electrode 416 which does not have isolation band 418extending to the end of first differential plate 410. Seconddifferential conductive band 406 is electrically isolated from commonplate 412 and first differential plate 410 due to isolation band 422 and428 respectively. In a similar fashion to that just described, seconddifferential conductive band 406 including end 432 is electricallycoupled to conductive electrode 426 of second differential plate 414.Due to isolation bands 420 and 418 of common plate 412 and firstdifferential plate 410, second differential conductive band 406 iselectrically isolated from first differential plate 410 and common plate412.

Electrical coupling of common conductive band 402 to common plate 412 isaccomplished by the physical coupling of sides 436 of common conductiveband 402 to common conductive electrode 424 which lacks isolation bandsalong the sides of common plate 412. To maintain electrical isolation ofcommon conductive electrode 424 from first and second differentialconductive bands 404 and 406, isolation bands 420 and 422 of commonplate 412 prevent any physical coupling of ends 432 and 434 of first andsecond differential conductive bands 404 and 406 with common conductiveelectrode 424.

As with the other embodiments of the differential and common mode filterof the present invention, conductive electrodes 416 and 426 of first andsecond differential plates 410 and 414 act as a line-to-linedifferential mode capacitor when electrical conductors are coupled tofirst and second differential conductive bands 404 and 406.Line-to-ground decoupling capacitors are formed between each conductiveelectrode, 416 and 426 respectively, and common conductive electrode 424which provides the inherent ground.

FIG. 11 shows surface mount differential and common mode filter 438which is a further embodiment of the filter shown in FIG. 10. Thecutaway perspective view more clearly shows how first and seconddifferential conductive bands 446 and 450, electrically connect toelectrode plates 448 and 452. Electrical connection between commonconductive band 442 and common ground conductive plates 440 is alsoshown with the only difference being that common conductive band 442 isnot continuous for 360° around the body of surface mount filter 438 aswas shown in FIG. 10.

Another striking difference between filter 438 of FIG. 11 and filter 400of FIG. 10 is that filter 438 is comprised of a plurality of electrodeand common ground conductive plates 448, 452, and 440. The advantage tousing a plurality of common ground conductive and electrode plates isthat greater capacitance values are obtained while keeping the size ofsurface mount filter 438 to a minimum. Capacitors, like resistors, canbe placed in series and in parailel. While the overall resistance of aplurality of resistors in series is the sum of their individual values,the opposite relationship exists for capacitors. To achieve an additiveeffect capacitors must be placed in parallel with one another whichfilter 438 does by having a plurality of plates coupled to first andsecond differential conductive bands 446 and 450 and common conductiveband 442. As in previous embodiments, material 454 having desiredelectrical properties surrounds and isolates the plurality of electrodeplates 448 and 452 and common ground conductive plates 440 from oneanother while imparting its corresponding electrical properties to thedifferential and common mode filter arrangement. FIG. 11b shows aschematic equivalent for surface mount differential and common modefilter 438 and the relationship between the plurality of common groundconductive plates 440 and the plurality of electrode plates 448 and 452.

Electrode plates 448 and 452 are each electrically coupled to theirrespective conductive bands, 450 and 446. Electrical conductors are thencoupled to first and second differential conductive bands 446 and 450with a plurality of electrode plates 448 and 452 acting in parallel toprovide one overall capacitive value coupled between the electricalconductors providing line-to-line differential mode coupling. Theplurality of common ground conductive plates 440 act in conjunction withelectrode plates 448 and 452 to provide line-to-ground decouplingcapacitors between each electrical conductor and common conductive band442. The plurality of common ground conductive plates 440 serve as theinherent ground which also may be connected to signal or earth groundthrough common conductive band 442. Again, the physical architecture ofthe present invention allows for numerous variations and by changing thenumber of plates and/or their sizes, a wide range of capacitive valuesand filter characteristics may be obtained.

FIG. 12 shows an alternative multi-component surface mount differentialand common mode filter which combines two individual filters into oneelectronic component. It should be understood that any number ofindividual filters can be incorporated into a single electroniccomponent and that the invention is not limited to two individualfilters. FIG. 12a shows one interconnect arrangement with FIG. 12bthrough 12 e disclosing the internal electrode and common groundconductive layers. First and second differential conductive bands 154and 156 are coupled to electrode plates 153 and 155 respectively andbands 154′ and 156′ are similarly coupled to electrode plates 153′ and155′. Multi-component surface mount filter 160 is also comprised ofmaterial 166 having predetermined electrical properties, as describedpreviously, disbursed in between the plurality of electrode and commonground conductive layers. Common ground conductive band 164 iselectrically connected to common ground conductive plate 163. Whatshould be noted is that not only does Applicant contemplate multiplecomponents within a single electronic package but that the shape andarrangement and/or length and width of first and second differentialconductive bands 154 and 156 and common conductive band 164 may bevaried to accompany any type of printed circuit board footprintdesirable. The conductive and common bands are only required to beelectrically coupled to the associated electrode plates and commonground conductive plate 163 while maintaining electrical isolation amongone another. The concept disclosed in FIG. 12 could just as easily beextended to incorporate 10, 20 or 100 differential and common modefilters if desired. Multi-component surface mount differential andcommon mode filter 160 is particularly useful for providing filtering tolarge data buses typically consisting of 32 or 64 data lines. These databuses handle digital information at extremely high frequencies emittinglarge amounts of electromagnetic energy and are also extremelysusceptible to over currents and voltage surges which can damagecircuitry and distort data.

FIGS. 23 and 24 disclose applications for the previously describedsurface mount filter, shown in FIG. 11. including electricalrepresentations of the applications. FIG. 23 shows the combination ofdifferential and common mode MOV filter 400 a coupled in parallel withdifferential and common mode capacitive filter 400 b which provides bothdifferential and common mode surge protection with increased capacitancenormally not obtainable with MOV devices alone. FIG. 23b shows filters400 a and 400 b physically stacked together such that first differentialconductive bands 446 a and 446 b are electrically coupled to one andanother, second differential conductive bands for 450 a and 450 b areelectrically coupled to one and another and common conductive groundbands 442 a and 442 b are electrically coupled to each another andrepresented as 443. As the physical construction of filters 400 a and400 b are identical, with the exception being the electricalcharacteristics of the material in each used to separate the variousconductive electrodes, isolation bands 444 a and 444 b of both filtersare also aligned. Although not shown, Applicant contemplates componentsof the present invention that are not physically identical also beingstacked or combined dependent upon the particular application in whichthe components are used. The benefit of the physical configuration ofsurface mount filters or components of the present invention is thatthey can be stacked saving space within circuits consistent with thetrend in modem electronics of miniaturization.

The result is shown in FIG. 23a where electrical conductors (not shown)would be coupled between first differential conductive bands 446 a and446 b and second differential conductive bands 450 a and 450 b resultingin differential and common mode filtering and surge suppression. Thiscombination improves overall filter response due to the increasedcapacitance combined with over voltage and surge protection. FIG. 24shows an alternate application in which surface mount capacitor 720 iscoupled between first and second differential conductive bands 446 and450 of differential and common mode MOV surge/filter 400 a with theresulting electrical representation showing the line-to-line capacitanceprovided by capacitor 720. This circuit configuration again increasesthe effective capacitance of differential and common mode MOVsurge/filter 400 a. As in FIG. 23, electrical conductors (not shown) arecoupled between the combination of first differential conductive band446 and first conductive band 724 and the combination of seconddifferential conductive band 450 a and second conductive band 722.

FIGS. 38 through 40 takes the component stacking shown in FIGS. 23 and24 one step further by stacking two or more differential and common modefilters within a single component package. Multi-component filter 806,shown in FIG. 38, is configured in the same manner as the numerous otherembodiments of the present invention except that the number of plates isdoubled, tripled or multiplied by the number of components being stackedwithin a single component package. FIG. 38 shows the various plateswhich make up first and second filters 814 and 816 of multi-componentfilter 806 with the point of division between the two filters shown bydashed line 818. Both the first and second filters 814 and 816 areconstructed in a similar manner. Each filter is comprised of a pluralityof common ground conductive plates 808 with different first and secondelectrode plates, 810 and 812 for filter 814 and 811 and 813 for filter816, sandwiched in between the various common ground conductive plates808. Each of the common ground conductive plates 808 and the first andsecond electrode plates, 810 through 812, are imprinted or etched upon asupport material having predetermined electrical properties usingvarious techniques known in the art. When the various layers are stackedadditional material having predetermined electrical properties (notshown) is disposed between and electrically isolates the various groundand electrode plates from one another.

As shown in FIG. 39, the result of internally stacking first and secondfilters 814 and 816 is that two or more differential and common modefilters are coupled in parallel. Multi-component filter 806, shown inFIGS. 39 and 40, is made up of first and second filters 814 and 816 withthe first electrode plates of each filter, 810 and 811, commonly coupledto first differential conductive band 822, the second electrode platesof each filter, 812 and 813, commonly coupled to second differentialconductive band 824 and all of the various common ground conductiveplates commonly coupled to common ground conductive band 820. FIG. 40shows an isometric view of a standard surface mount component package inwhich multi-component filter 806 is enclosed within. The package iscovered by insulated outer casing 826 except for the various conductivebands used for electrically coupling filter 806 with external circuitry.

While only two filters are shown internally stacked within a singlecomponent package, Applicant contemplates additional components beinginternally stacked and does not intend to be limited to the embodimentshown in FIGS. 38 through 40. One particular application of the internalstacking technology is in the combination of a high capacitance filtercoupled with a low capacitance filter which results in a broad bandfilter having improved filter performance across a broader frequencyrange. Referring to FIG. 38, first and second differential plates 811and 813 of second filter 816 include smaller conductive surfaces 830than the conductive surfaces 828 found in first filter 814. By varyingthe size of the conductive surfaces of the first and second differentialplates, actual capacitance values of the filters can be varied.Multi-component filter 806 is the combination of high capacitance filter814 and low capacitance filter 816 with the combination providing asingle multi-component filter 806 providing the benefits of a highcapacitance filter with improved high frequency performance.

FIG. 25 discloses a further alternate application which combinesdifferential and common mode filter 10, as shown in FIG. 1, coupled withtwo MOV electrode plates 700, one on top 820 of filter 10 and one onbottom 822 of filter 10, to form a filter which combines differentialand common mode surge protection and capacitive filtering as shown withreference to FIG. 23. The combination as shown in FIG. 25a provides thefurther advantage of allowing both filter and MOV components to becombined while the combination allowing for through-hole coupling ofelectrical conductors 12 a and 12 b. The embodiment shown in FIG. 23 didnot require separate MOVs because it was configured for surface mounttechnology in accordance with the present invention. The embodimentshown in FIG. 25a is necessary because MOV components havingthrough-hole coupling apertures are generally not available due to thedetrimental effect the apertures have on the overall operating and costcharacteristics of the MOVs. To allow for electrical coupling of MOVs700 to the electrode plates internal to differential and common modefilter 10, shown in FIG. 1, several surface modifications to filter 10are necessary. The top 820 and bottom 822 of differential and commonmode filter 10 have been modified, as shown in FIG. 25c, to replace oneinsulating aperture 18 with through-hole plated coupling aperture 718.Through-hole plated coupling aperture 718 of top 820 and bottom 822 arepositioned so that each corresponds with opposite electrical conductors12 a or 12 b. Although not shown, each through-hole plated couplingaperture 718 is electrically connected to one of the two electrodeplates embedded within differential and common mode filter 10 therebyallowing electrical connection of electrical conductors 12 a and 12 b tothe respective electrode plates which form a line-to-line differentialcapacitor between conductors 12 a and 12 b. To allow for coupling of MOV700 to the top and bottom of differential and common mode filter 10,through-hole plated coupling aperture 718 includes strip 824 ofconductive material to which one of the two contacts of each MOV 700 iselectrically connected. Each MOV 700 includes two terminals 828 and 830to which MOV 700 electrically couples to other circuits. As shown inFIG. 25a, terminals 830 of both MOVs 700 are physically and electricallycoupled to conductive surface 826 of differential and common mode filter10 through standard means such as application of solder 710. Conductivesurface 826 of differential and common mode filter 10 is electricallycoupled to common ground conductive plates 14 as shown in FIG. 1.Terminals 828 of each MOV 700 are physically and electrically coupled bysolder 710 to conductive strip 824 which connects terminals 828 with therespective electrical conductor 12 a and 12 b which in turn is connectedto the internal electrode plates of differential and common mode filter10. The result is shown in FIG. 25b and consists of the combination ofdifferential and common mode MOV surge protection in parallel withdifferential and common mode capacitive filtering between terminals 716a and 716 b to which electrical conductors 12 a and 12 b areelectrically coupled.

FIGS. 29 and 30 show a further alternative multi-component surface mountdifferential and common mode filter designed to provide a strip offilters for varied use. This specific design is for use with multiconductor electronic connectors. As in other embodiments of the presentinvention, strip filter 642 is comprised of a plurality of common groundconductive plates 656 with first and second electrode plates 662 and 664sandwiched in between the various common ground conductive plates 656.Strip filter 642, shown in FIG. 29, has four sets of differential andcommon mode filters. Each common ground conductive plate 656 is etchedupon support material 616 having predetermined electrical properties, asdisclosed throughout the specification, so that portions of material 616act as insulation on either side of each common ground conductive plate656 with only ground extensions 660 extending to the edges of supportmaterial 616. The various first and second electrode plates 662 and 664are also formed on strips of support material 616 so that each electrodeplate is surrounded by material 616 except for electrode extensions 666which extend to the edges of support material 616. As can be seen inFIG. 29, each electrode extension 666 of each first electrode plate 662extends in an opposite direction from the electrode extension 666 of thecorresponding second electrode plate 664. The arrangement of groundextensions 660 and electrode extensions 666 can be reconfigured innumerous patterns as long as a convenient layout for electricalconductor coupling is created As in the various other embodiments of thepresent invention, each differential and common mode filter included instrip filter 642 consists of a first and second electrode plate 662 and664 sandwiched between common ground conductive plates 656 withadditional material having predetermined electrical properties (notshown) disposed between and electrically isolating the various groundand electrode plates from one another. FIG. 30 shows top, bottom andside views of strip filter 642 having first and second differentialconductive bands 652 and 654 running perpendicular to the lengths ofsupport material 616 and slightly overlapping onto the top of stripfilter 642, as shown in FIG. 30a. The bottom of strip filter 642, asshown in FIG. 30d, is the same as the top to allow for surface mountingof strip filter 642. Common ground conductive bands 650 extendvertically up the ends and onto the top and bottom of strip filter 642,as indicated by the portions labeled 650 in FIGS. 30a and 30 d.Additional common ground conductive bands 650 are also found on the topand bottom of strip filter 642 but in this configuration they do notextend down the sides. First and second differential conductive bands652 and 654 extend down the corresponding sides of strip filter 642allowing the various electrode extensions 666 of each of the first andsecond electrode plates 662 and 664 to electrically couple to theirrespective conductive bands thereby allowing connection of externalelectrical conductors to the various internal electrode plates of stripfilter 642. For purposes of clarity, the corresponding first and secondelectrode plates 662 and 664 and first and second differentialconductive bands 652 and 654 include suffix designations (a) through (d)which represents each of the four differential and common mode filtersincluded within strip filter 642. FIG. 31 is a further example of stripfilter 642 which includes an additional first electrode plate 662 e. Byadding an additional electrode plate strip filter 642 can now accomodatean odd number of electrical conductors. An example of an applicationrequiring an odd number of electrical conductors is providing filteringfor D-sub connectors which typically have 9 or 15 conductors. While notshown, the only difference in the top, bottom and side views of stripfilter 642, shown in FIG. 31, is that an additional conductive band 652and one or more common ground conductive bands 650 would be added toaccomodate the coupling of the additional conductors. By adding firstelectrode plate 662 e without a corresponding second electrode plate,electrode plate 662 e forms a line-to-ground capacitor between itselfand the plurality of common ground conductive plates 656. Although acorresponding second electrode plate to first electrode plate 662 e ismissing, differential and common mode filtering still takes placebetween the electrical conductor that is connected to first electrodeplate 662 e and any one of the electrical conductors coupled to secondelectrode plates 664 a-d.

FIGS. 32 through 37 show a number of variations of the multi-componentsurface mount differential and common mode strip filters shown in FIGS.29 through 31. Referring to FIGS. 32 and 33, strip filter 800 iscomprised of a plurality of common ground conductive plates 656 withfirst and second electrode plates 662 and 664 sandwiched in between thevarious common ground conductive plates 656. As in the previousembodiments, strip filter 800 has four pairs of contacts for the samedifferential and common mode filter, 1A, 4A, 5A and 8A for electrodeplate 662 and 2B, 3B, 6B and 7B for electrode plate 664. Each commonground conductive plate 656 is etched upon support material 616 havingpredetermined electrical properties, as disclosed throughout thisspecification, so that portions of material 616 act as insulation oneither side of each common ground conductive plate 656. Unlike theembodiments shown in FIGS. 29 through 31, each of the common groundconductive plates 656 has portions of materials 616 extending lengthwiseon either side of common ground conductive plate 656. The first andsecond electrode plates 662 and 664 are also formed on strips of supportmaterial 616 so that the electrode plates are surrounded by material 616except for electrode extensions 666 which extend to the edges of supportmaterial 616. Additional material having predetermined electricalproperties (not shown) is disposed between and electrically isolates thevarious common ground conductive plates 656 and electrode plates 662 and664, all from one another. Strip filter 800 is advantageous in that itprovides greater connection versatility with low inductance.

FIG. 33 shows top, bottom and side views of strip filter 800 havingfirst and second differential conductive bands 652 and 654 runningperpendicular to the lengths of support material 616 and slightlyoverlapping onto the top of strip filter 800, as shown in FIG. 33a. Thebottom of strip filter 800, as shown in FIG. 33d, is the same as the topto allow for surface mounting of strip filter 800. Common groundconductive bands 650 extend vertically up the ends and onto the top andbottom of strip filter 800, as shown in FIGS. 33a, 33 d and 33 e. Firstand second differential conductive bands 652 and 654 extend down thecorresponding sides of strip filter 800 allowing the various electrodeextensions 666 of each of the first and second electrode plates 662 and664 to electrically couple to their respective conductive bands therebyallowing connection of external electrical conductors to the first andsecond internal electrode plates.

FIGS. 34 and 35 show a further embodiment of the present invention instrip filter 802 with the only difference being the actual configurationand orientation of the various electrode extensions 666 of each of thefirst and second electrode plates 662 and 664. As clearly shown in FIGS.32 through 35, the connection or pinout configurations of the stripfilters can be arranged to suit any application. Strip filter 804, asshown in FIGS. 36 and 37, is a further embodiment which emphasizes thecommon ground connection. Referring to FIG. 36, each common groundconductive plate 656 is imprinted or etched upon support material 616having predetermined electrical properties through techniques known inthe art, so that an elongated strip of material 616 acts as insulationalong one side of each common ground conductive plate 656. The first andsecond electrode plates 662 and 664 are essentially the same as in theprevious embodiments except that electrode extension 666 of both thefirst and second electrode plates 662 and 664 extend from the same sideof the electrode plates as the insulation strips 616 extend on each thecommon ground conductive plates 656. FIG. 37 shows top, bottom, side andend views of strip filter 804 having first and second differentialconductive bands 652 and 654 running perpendicular to the lengths ofsupport material 616 and slightly overlapping onto the top of stripfilter 804, as shown in FIG. 37a. The bottom of strip filter 804, asshown in FIG. 37d, is the same as the top to allow for surface mountingof strip filter 804. In this embodiment, common ground conductive band650 extends vertically up the ends and onto the top and bottom of stripfilter 804 and entirely encompasses one side of strip filter 804, asshown in FIG. 37c. As with the first and second differential conductivebands 652 and 654, the common ground conductive band 650 also extendsonto the top and bottom of strip filter 804 along the full length of thecovered side. The configuration of strip filter 804 is particularlyuseful in applications requiring a large ground plane which acts as ashield and is capable of absorbing and dissipating greater amounts ofheat and electromagnetic interference.

FIGS. 14 and 15 disclose a further embodiment of a differential andcommon mode filter formed on a film or Mylar-like medium. Thisembodiment is comprised of a film medium and consists of a common groundconductive plate 480 followed by the first electrode differential plate460, then another common ground conductive plate 480 and secondelectrode differential plate 500, then another common ground conductiveplate 480. Each plate is essentially comprised of film 472, which itselfmay be comprised of a number of materials such as but not limited toMylar, wherein film 472 is completely metallized on one side creating ametallized plate. Using lasers, portions of metallized material areremoved (demetallized) in predetermined patterns to create isolationbarriers. First differential plate 460 has two laser edged isolationbarriers 462 and 466, which divide first differential plate 460 intothree conductive areas: electrode 464, isolated electrode 468 and commonelectrode 470. Second differential plate 500 is identical to firstdifferential plate 460 in that it has two isolation barriers 506 and 504which divide second differential plate 500 into three conductive areas:electrode 510, isolated electrode 502 and common electrode 508. For bothfirst and second differential plates 460 and 500, isolation barriers 462and 506 are essentially U-shaped to create electrodes 464 and 510 whichencompass a large area of first and second plates 460 and 500. U-shapedisolation barriers 462 and 506 allow electrode 464 and 510 to extendfully to ends 476 and 514, respectively. Extending from isolationbarrier 462 and 506 are members 474 and 512 and extending from isolationbarriers 466 and 504 are members 473 and 513. Members 474 and 512 extendperpendicular to and outward from the ends of unshaped isolationbarriers 462 and 506 at their points nearest ends 476 and 514 andmembers 473 and 513 extend perpendicular to and outward from isolationbarriers 466 and 504 respectively in order to fully isolate commonelectrodes 470 and 508 from ends 476 and 514. Also, both first andsecond differential plates 460 and 480 have isolated electrodes 468 and502 formed on opposite of ends 476 and 514 by isolation barriers 466 and504.

Common ground conductive plate 480 includes isolation barriers 482 and492 which divide common ground conductive plate 480 into threeconductive surfaces: common electrode 488, isolated electrode 484 andisolated electrode 494. As shown, isolation barriers 482 and 492 runvertically adjacent to and in parallel with the right and left edges ofcommon ground conductive plate 480. Both isolation barriers 482 and 492also include members 496 extending outward and perpendicular from thevertical sections of isolation barriers 482 and 492 and are positionedso when plates 460, 480 and 500 are stacked, they are aligned with thehorizontal portions of the U-shaped isolation barriers 462 and 506 offirst and second differential plates 460 and 500.

An additional feature is that common ground conductive plate 480 can beoptimized for use in filtering AC or DC signals. Isolation barriers 492and 482 as described above are optimized for use in filtering DCsignals. For DC operation isolated electrodes 484 and 494 require verylittle area within common ground conductive plate 480. When the filteris comprised of a film medium and used for filtering AC signals,isolated electrodes 484 and 494 require a greater area which isaccomplished by etching modified isolation barriers 486 and 490. Thevertically running isolation barriers 484 and 494 are etched closertogether and closer to the center of common ground conductive plate 480.To accommodate this modification, members 496 extending outward andperpendicular from the vertical sections are longer than for the DCversion. The greater area isolated electrodes 484 and 494 provide betterAC filtering characteristics, although either configuration providesfiltering to both types of current.

FIG. 15 is a cross-section of film medium differential and common modefilter 540 comprised of a plurality of plates similar to those shown inFIG. 14. As for the surface mount chip embodiment shown in FIG. 11, filmdifferential and common mode filter 540 can also consist of more thanfive plates in effect coupling capacitors in parallel to increaseoverall capacitance.

The top and bottom of filter 540 consist of protective cover layers 555.Situated below the top protective cover layer 555 is common groundconductive plate 480, followed by an electrode plate 460, followed byanother common ground conductor plate 480, followed by the nextelectrode plate 500 and then another common ground conductive plate 480.The previous sequence of alternating ground and electrode plates can berepeated to achieve additional capacitance. Shown in cross section eachlayer or plate is comprised of a film 558 possessing a conductivemetalized upper surface 556 which have isolation patterns cut into themetal surface with a laser creating isolation patterns 554. Terminalconductive blocks 550 and 552 are comprised of pure aluminum which isdeposited on the edges and penetrates into the film extensions toprovide a highly conductive termination consisting of like metals. Theextensions described are created by stacking the different plates in asequence that has every electrode plate 460 or 500 surrounded by commonground conductive plates 480 as pictured in FIG. 15. The electrodeplates 460 and 500 are offset from each other and the common groundconductive plates to facilitate edge termination.

FIGS. 16 through 19 are directed towards embodiments of the differentialand common mode filter configured and optimized for use with electricmotors. Electric motors are a tremendous source of electromagneticemissions. This fact is evident even to layman, as most people haveexperienced running a vacuum cleaner in front of an operating televisionset and noticing “snow” fill the screen. This interference with thetelevision is due to the electromagnetic emissions from the motor.Vacuum cleaners are by no means the only source of electromagneticemissions. Electric motors are used extensively in a number of homeappliances such as washing machines, dryers, dishwashers, blenders, hairdryers. In addition, most automobiles contain a number of electricmotors to control the windshield wipers, electric windows, electricadjustable mirrors, retractable antennas and a whole host of otherfunctions. Due to the prevalence of electric motors and increasedelectromagnetic emissions standards there is a need for differential andcommon mode filtering.

Electric motor filter 180 may be made in any number of shapes but in thepreferred embodiment shown in FIG. 16 it is essentially a rectangularblock comprised of material 182 having one of a number of predeterminedelectrical properties. FIG. 16a shows the outer construction of filter180 which consists of a rectangular block of material 182 having aninsulated shaft aperture 188 disposed through filter 180's center,conductive bands 184 and 194 and common conductive bands 186. FIG. 16bshows a side view of filter 180 with the arrangement of conductive bands184 and 194 and common conductive band 186 being electrically andphysically isolated from one another by sections of material 182positioned between the various bands. FIG. 16c shows a cross sectionalong line A of FIG. 16a. As in all previous embodiments, the physicalarchitecture of the present invention is comprised of conductiveelectrodes 181 and 185 with common conductive electrode 183 sandwichedin between. Material 182 having predetermined electrical properties isinterspersed between all of the electrodes to prevent electricalconnection between the various conductive electrodes 181 and 185 andcommon conductive electrode 183. Similar to that of the surface mountembodiments of the present invention, filter 180 employs conductivebands 184 and 194 to electrically connect filter 180's internalelectrodes to electrical conductors. Conductive electrode 181 extendsfully to and comes in contact with conductive band 184 to provide theelectrical interface required. As shown in FIG. 16c, conductiveelectrode 181 does not extend fully to come in contact with conductiveband 194 which is coupled to conductive electrode 185. Although notshown, common conductive electrode 183 extends fully between commonconductive bands 186 without coming in contact with conductive bands 184and 194. Again, by coupling common conductive bands 186 to signal orearth ground, a “true” ground may be employed rather than the inherentground provided by common conductive electrode 183.

FIG. 16d is a schematic representation of differential and common modeelectric motor filter 180 showing conductive electrodes 181 and 185providing the two necessary parallel plates for a line-to-linedifferential mode coupling capacitor while at the same time working inconjunction with common conductive electrode 183 to provideline-to-ground common mode decoupling capacitors with common conductiveelectrode 183 acting as the inherent ground. Also shown are conductivebands 184, 194 and common conductive band 186 which allow electric motorfilter 180 to be connected to external electrical conductors. While thepreferred embodiment of FIG. 16 only shows one common conductiveelectrode 183 and two conductive electrodes 181 and 185, Applicantcontemplates the use of a plurality of electrodes to obtain varyingcapacitance values through the additive effect of parallel capacitancesimilar to that described for previous embodiments.

FIG. 17 shows differential and common mode electric motor filter 180electrically and physically coupled to electric motor 200. As shown inFIG. 17a, electric motor filter 180 is placed on top of electric motor200 having motor shaft 202 extending outward therefrom. Motor shaft 202is disposed through shaft aperture 188 of filter 180 with conductivebands 184 and 194 electrically coupled to connection terminals 196,which are isolated from one another and the rotor of electric motor 200.The individual connection terminals 196, although not shown, are thenelectrically connected to electrical supply lines providing electricmotor 200 with power. Once electric motor filter 180 isconnected/coupled to electric motor 200, motor face plate 208 is placedon top of both motor 200 and filter 180 with motor shaft 202 disposedthrough a similar aperture in the center of motor face plate 208. Faceplate 208 is then physically coupled to the body of motor 200 throughthe use of clamps 206. While not shown, filter 180 may be used with itsinherent ground by coupling common conductive bands 186 to the motorsenclosure or common conductive bands 186 may be directly wired tocircuit or earth ground.

FIG. 18 is a logarithmic graph showing a comparison of electric motor200's electromagnetic emission levels as a function of frequency withthe result of an electric motor having a standard filter being shown at220 and the results of differential and common mode electric motorfilter 180 shown at 222. The graph demonstrates that between 0.01 MHzand approximately 10 MHz there is a minimum of a 20 dB suppression ofelectromagnetic emissions throughout the range with even more pronounceddecreases in the 0.1 to 1 MHz range. One can see that at the upperfrequency range of 10-20 MHz and beyond, the decrease in electromagneticemissions is not as great as at the lower frequencies but this is notparticularly critical as most electric motors operate well below thisfrequency range thereby allowing electric motor filter 180 to provideenhanced performance with decreased electromagnetic emissions for themajority of applications.

Differential and common mode electric motor filter 230 shown in FIG. 19is a further embodiment of the filter of FIG. 16. The multi-plateembodiment of FIG. 19 is almost identical to the filter embodiment shownand described in FIG. 1 with the exceptions being the shapes of theplurality of plates and that each plate includes motor shaft aperture242 to allow the plurality of plates and filter 230 itself to be coupledwith the top of an electric motor without interfering with the motorshaft and its rotation. FIG. 19a shows the individual plates of filter230 which include common ground conductive plate 232 and a plurality ofconductive plates 246 with all three plates having motor shaft apertures242. Common ground conductive plate 232 is comprised of a conductivematerial and in the preferred embodiment is fabricated from a piece ofmetal. All three plates have at least two apertures 252 which acceptelectrical conductors 244 as shown in FIG. 19b. The two conductiveplates 246 of FIG. 19a show opposite sides of plate 246. As in the otherembodiments already described, conductive plates 246 are fabricated ofmaterial 254 having predetermined electrical properties wherein one sideof plate 246 is covered by a conductive surface 236 with the other sideof plate 246 having a non-conductive surface 234. To provide electricalcoupling between each electrical conductor 244 and the appropriateconductive surface 236 of each conductive plate 246, one of the twoapertures 252 is a coupling aperture 240 while the other aperture 252 issurrounded by an insulating ring 238. Both apertures 252 within commonground conductive plate 232 are surrounded by insulating rings 238 toprevent any electrical connection between common ground conductive plate232 and either electrical conductor 244.

FIG. 19b shows the operative physical coupling of common groundconductive plate 232 and conductive plates 246. Common ground conductiveplate 232 is sandwiched between conductive plates 246 in such a way thatnon-conductive surface 234 of each conductive plate 246 is facing andcomes in contact with one of the two sides of common ground conductiveplate 232. Conductive plates 246 are also arranged so that insulatingrings 238 of each plate 246 are positioned so only one of the twoelectrical conductors 244 is coupled to either conductive surface 236 ofconductive plates 246. Once common ground conductive plate 232 and theplurality of conductive plates 246 are physically coupled the entirearrangement which makes up differential and common mode electric motorfilter 230 is then placed over the top of an electric motor with themotor shaft extending through shaft apertures 242 of each of the plates.

FIG. 19c is a schematic representation of the filter components showinghow the individual conductive surfaces of the plurality of platesinteract to form the line-to-line and line-to-ground capacitors whichform filter 230. Because the plurality of conductive plates 246 areessentially identical and are just arranged differently with respect tocommon ground conductive plate 232, the schematic shown in FIG. 19c usesprime reference numerals to indicate conductive surfaces 236 of theindividual conductive plates 246.

FIGS. 20 and 21 show a high-power embodiment of the differential andcommon mode filter of the present invention. FIG. 20a shows aquasi-schematic representation of the physical arrangement of plateswhich make up the filter shown in FIG. 20b. Referring to both FIGS. 20aand 20 b it can be seen that common ground conductive plate 292 is againsandwiched between two conductive electrode plates, 270 and 270′, whichare individually connected/coupled to electrical conductors 275 a and275 b. Each conductive electrode plate, 270 and 270′, consists of amaterial 264 having specific predetermined properties, with each platethen having a conductive surface to which electrical connections aremade. After electrical conductors 275 a and 275 b are connected toconductive electrode plates 270 and 270′, the conductive surface iscoated with insulation. Conductive electrode plates 270 and 270′ arephysically coupled to common ground conductive plate 292 via typicaladhesive material known in the art. A clearer representation ofhigh-power differential and common mode filter 260 is shown in FIG. 21with FIG. 21a showing the physical embodiment and FIG. 21b showing arepresentative schematic. Filter 260, as shown in FIG. 21a, is comprisedof common ground conductive plate 262 sandwiched between wheels ofmaterial 264 having predetermined electrical properties. Wheels 264 ofmaterial are held in place by conductive electrodes 270 and 270′ withcoupling axle 278 disposed through the plurality of apertures 266, notshown, and disposed through wheels 264 and common ground conductiveplate 262. To manage the higher current and voltage conditions filter260 is designed for, common ground conductive plate 262, conductiveplates 270 and 270′ and wheels of material 264 are typically sized muchlarger than previous embodiments of the present invention. To allowfilter 260 to be connected to external electrical conductors, conductiveelectrodes 270 have connecting members 284 extending therefrom which aremechanically coupled to connection terminals 275 a and 275 b throughcommon means such as tightening screws and washers. Connection terminals275 a and 275 b are mounted on top of enclosure lid 282 to create a onepiece assembly consisting of enclosure lid 282, common ground conductiveplate 262, conductive electrodes 270 and 270′ and wheels 264 ofmaterial. This single component is then placed within componentenclosure 276 which has flanges 272 extending from common groundconductive plate 262 coupled to enclosure mounting holes 280. Thisarrangement provides a means of coupling the inherent ground provided bycommon ground conductive plate 262 to circuit or earth ground ifdesired. FIG. 21b shows the relationship of the different physicalcomponents of FIG. 21a that make up filter 260 schematicallyrepresented. As in all other embodiments of the present invention,conductive electrodes 270, represented with and without a prime toindicate separate surfaces, make up the two parallel plates necessaryfor a line-to-line capacitor coupled between connection terminals 274.Conductive electrodes 270 individually but in conjunction with commonconductive electrode 262 make up line-to-ground common mode decouplingcapacitors with common conductive electrode 262 acting as the inherentground.

As can be seen, many different applications of the differential andcommon mode filter architecture are possible and review of severalfeatures universal to all the embodiments must be noted. First, thematerial having predetermined electrical properties may be one of anumber in any of the embodiments including but not limited to dielectricmaterial, metal oxide varistor material, ferrite material and other moreexotic substances such as Mylar film or sintered polycrystalline. Nomatter which material is used, the combination of common groundconductive plates and electrode conductive plates creates a plurality ofcapacitors to form a line-to-line differential coupling capacitorbetween and two line-to-ground decoupling capacitors from a pair ofelectrical conductors. The material having electrical properties willvary the capacitance values and/or add additional features such asover-voltage and surge protection or increased inductance, resistance,or a combination of all the above.

Second, in all embodiments whether shown or not, the number of plates,both common conductive and electrode, can be multiplied to create anumber of capacitive elements in parallel which thereby add to createincreased capacitance values.

Third, additional common ground conductive plates surrounding thecombination of a center conductive plate and a plurality of conductiveelectrodes may be employed to provide an increased inherent ground andsurge dissipation area and a true Faraday shield in all embodiments.Additional common ground conductive plates can be employed with any ofthe embodiments shown and is fully contemplated by Applicant.

Finally, from a review of the numerous embodiments it should be apparentthat the shape, thickness or size may be varied depending on theelectrical characteristics desired or upon the application in which thefilter is to be used due to the physical architecture derived from thearrangement of common ground conductive and conductive electrode plates.

In fact the differential and common mode filter, although not shown,could easily be fabricated in silicon and directly incorporated intointegrated circuits for use in such applications as communication chips.The differential and common mode filter would be embedded and filtercommunication or data lines directly from their circuit board terminalconnections, thus reducing circuit board real estate requirements andfurther reducing overall circuit size while having simpler productionrequirements. Integrated circuits are already being made havingcapacitors etched within the silicone foundation which allows thearchitecture of the present invention to readily be incorporated withtechnology available today.

Although the principals, preferred embodiments and preferred operationof the present invention have been described in detail herein, this isnot to be construed as being limited to the particular illustrativeforms disclosed. It will thus become apparent to those skilled in theart that various modifications of the preferred embodiments herein canbe made without departing from the spirit or scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A line conditioning electronic componentcomprising: at least three common ground conductive plates formed upon asupport material having predetermined electrical properties; first andsecond electrode plates, wherein said first electrode plate is formedupon a first support material having predetermined electrical propertiesand said second electrode plate is formed upon a second support materialhaving predetermined electrical properties; wherein said first electrodeplate is stacked between at least two common ground conductive plates ofsaid at least three common ground conductive plates and said secondelectrode plate is stacked between at least two common ground conductiveplates of said at least three common ground conductive plates, whereinsaid first electrode plate and said second electrode plate sandwich atleast one center common ground conductive plate of said at least threecommon ground conductive plates; wherein said support material isolatessaid at least three common ground conductive plates, said firstelectrode plate and said second electrode plate preventing directelectrical connection between said plates; and said at least threecommon ground conductive plates, said first electrode plate, said secondelectrode plate and said support material form a plurality ofdifferential and common mode filters.
 2. The line conditioningelectronic component recited in claim 1, wherein said at least threecommon ground conductive plates are conductively connected electricallycommon to each other.
 3. A line conditioning electronic componentcomprising: at least three common-sized electrodes each conductivelyconnected electrically common to each other and formed upon a supportmaterial having predetermined properties; at least a first electrode andat least a second electrode, each common-sized to the other and formedupon said support material having predetermined properties; wherein saidat least a first electrode plate is stacked between at least twocommon-sized electrodes of said at least three common-sized electrodesand said at least a second electrode plate is stacked between at leasttwo common-sized electrodes of said at least three common-sizedelectrodes, wherein said at least a first electrode plate and said atleast a second electrode plate sandwich at least one centeredcommon-sized electrode of said at least three common-sized electrodes;wherein said support material isolates said at least three common-sizedelectrodes from said at least a first electrode and said at a leastsecond electrode preventing a direct connection between said electrodes;and said at least three common-sized electrodes, said at least firstelectrode, said at least second electrode and said support materialhaving predetermined properties form at least one differential andcommon mode filter.
 4. A conditioning component comprising: a pluralityof common electrodes conductively connected to each other including atleast a first common electrode, a second common electrode, and a thirdcommon electrode; a first differential electrode and a seconddifferential electrode; said first differential electrode and saidsecond differential electrode are interspersed within said plurality ofcommon electrodes such that said first differential electrode is stackedbetween said first common electrode and said second common electrode andsaid second differential electrode is stacked between said second commonelectrode and said third common electrode; and a dielectric materialpositioned between said plurality of common electrodes and said firstdifferential electrode and said second differential electrode.